An electrophotographic photosensitive member using an organic photo-conductive material (organic electrophotographic photosensitive member) has been intensively studied and developed in recent years.
The electrophotographic photosensitive member basically includes a support and a photosensitive layer formed on the support. In actuality, however, various layers are provided in many cases between the support and the photosensitive layer for the purposes of, for example, covering defects in the surface of the support, protecting the photosensitive layer from electrical destruction, enhancing chargeability, and improving charge injection blocking property from the support to the photosensitive layer.
Of the layers to be provided between the support and the photosensitive layer, a layer containing metal oxide particles is known as a layer to be provided for the purpose of covering defects in the surface of the support. The layer containing metal oxide particles generally has high electro-conductivity (for example, an initial volume resistivity of 1.0×108 to 2.0×1013 Ω·cm) as compared to that of a layer not containing metal oxide particles, and even when the thickness of the layer is increased, a residual potential at the time of forming an image is difficult to increase. Therefore, the layer containing metal oxide particles covers defects in the surface of the support easily. When such layer having high electro-conductivity (hereinafter referred to as “conductive layer”) is provided between the support and the photosensitive layer to cover defects in the surface of the support, an allowable range of defects in the surface of the support is enlarged. As a result, an allowable range of the support to be used is enlarged. Thus, an advantage of enhancing productivity of an electrophotographic photosensitive member is provided.
Patent Literature 1 discloses a technology involving using, in a conductive layer between a support and a photosensitive layer, a titanium oxide particle coated with tin oxide doped with phosphorus or tungsten. In addition, Patent Literature 2 discloses a technology involving using, in a conductive layer between a support and a photosensitive layer, a titanium oxide particle coated with tin oxide doped with phosphorus, tungsten, or fluorine.
In addition, Patent Literature 3 discloses a technology involving incorporating, into the undercoat layer of an electrophotographic photosensitive member obtained by sequentially laminating the undercoat layer, an intermediate layer, and a photosensitive layer on a conductive support, two kinds of metal oxide particles having different average particle diameters. In addition, Patent Literature 4 discloses the following technology. Two or more kinds of electro-conductive particles having different primary particle diameters are incorporated into the intermediate layer of an electrophotographic photosensitive member obtained by laminating the intermediate layer and a photosensitive layer on a conductive support in the stated order, a ratio “A:B” between the average particle diameters of primary particles A having the largest average particle diameter of the electro-conductive particles and primary particles B having the smallest average particle diameter thereof is set to 12:1 to 30:1, and the average particle diameter of the primary particles B is set to 0.05 μm or less. In addition, Patent Literature 4 discloses a technology involving using a tin oxide particle doped with tantalum in the intermediate layer of the electrophotographic photosensitive member.
In addition, Patent Literatures 5 and 6 each describe a technology involving using a tin oxide particle doped with niobium in a conductive layer or an intermediate layer between a support and a photosensitive layer.